View Full Version : Volumetric Light behind HV Cloud

09-25-2003, 08:44 AM
I'am having trouble getting my volumetric light to render behind a HV Volume 'cloud' is there a workaround or fix? or is this a known problem?



09-25-2003, 09:27 AM
Do you have RayTrace Transperancy turned on?

09-25-2003, 09:39 AM
Hi Riki, I have raytrace 'everything' off at the moment.

09-25-2003, 09:58 AM
I don't know the answer, just a stab in the dark but try it with Ray Tracing Transperancy turned on. See if it makes any diference. Otherwise someone else might know??

09-26-2003, 02:51 AM
Thanks for trying riki, i've tried all the raytrace options in different combinations, nothing works, just another one of though's Lightwave quirks I guess.

I wonder if MAYA will do it we have a copy of 5 here?

Can anyone else replicate the problem?

Can anyone confirm this bug from Lightwave tech support perhaps?


09-26-2003, 02:54 AM
here's my test file.

09-26-2003, 03:46 AM

09-26-2003, 04:21 AM
Phew... ok... done it! ;)

I lost a little amount of time thinking it was a Light problem (and half it is): so I tested using "Cast Shadow Opacity" option but it's really not useful at all!

The trick it's really simple:
1 - first of all your light must have no Falloff or only Linear Falloff (both Inverse and Inverse^2 kills the effect). You can read about bad Falloffs here: http://vbulletin.newtek.com/showthread.php?s=&threadid=10715
2 - reduce the "Near Clip Distance" in the HV's "Shading/Advanced" tab to a smaller value; you actually have it at 1m (too big for your own scene)
3 - increase Volumetric Light's "Opacity" (this is useful to cut away the base of the cone in some circumstances).

Take a look at the picture (red light for better contrast):
- HV's Near Clip Distance at 20cm (you can test with little bigger values)
- Volumetric Light's "Height" at 15 m
- Volumetric Light's "Opacity" at 50%
- Volumetric Light's "Luminosity" at 500% (as you can see it works good also with high values)
- Light using Shadow Map (for faster rendering)
- "Render Option/Rendering/Ray Trace" all OFF

09-26-2003, 05:39 AM
Previous post updated... sorry... forgot about Light Falloff! :(


09-26-2003, 09:46 AM
Thanks Exper, I'am doing several more tests and i'll post the result next week.

09-26-2003, 12:36 PM
wizlon... you're welcome... ;)

Another little test...

09-27-2003, 05:27 AM
A short sequence here:


09-27-2003, 04:38 PM
I like that...especially near the end, the one frame where the light is pointed at the camera...looks very translucent....you should see how long it would take to render a real sky with alot of clouds and one volumetric sun lighting them the same way....

so how long does that take a frame? ...forever I bet....

09-29-2003, 01:47 AM
Exper, great tests, could you post me your scene files I need to compare some your settings against mine.

09-29-2003, 01:47 AM
HowardM... thanks!

Yes... I presume! :(

Previous short sequence required an average of 3m. 40s. per frame on a AthlonXP 2400+ with 768MB RAM system!

Ok wizlon!